package com.cyh.structurealgorithm;

import java.util.Arrays;

public class PrimAlgorithm {
    public static void test() {
        char[] data = new char[] {'A', 'B', 'C', 'D', 'E', 'F', 'G'};
        int verxs = data.length;
        int[][] weight = new int[][] {
                {10000, 5, 7, 10000, 10000, 10000, 2},
                {5, 10000, 10000, 9, 10000, 10000, 3},
                {7, 10000, 10000, 10000, 8, 10000, 10000},
                {10000, 9, 10000, 10000, 10000, 4, 10000},
                {10000, 10000, 8, 10000, 10000, 5, 4},
                {10000, 10000, 10000, 4, 5, 10000, 6},
                {2, 3, 10000, 10000, 4, 6, 10000},
        }; //10000表示两个村庄不连通。 横坐标和纵坐标都是A-G

        MGraph graph = new MGraph(verxs);
        MinTree minTree = new MinTree();
        minTree.createGraph(graph, verxs, data, weight);
        minTree.showGraph(graph);
        minTree.prim(graph, 0);
    }
}

//创建最小树--村庄图
class MinTree{
    /*
    * graph: 图对象
    * verxs: 图对应的顶点个数
    * data: 图各个顶点的值
    * weight: 图的邻接矩阵
    * */
    public void createGraph(MGraph graph, int verxs, char data[], int[][] weight) {
        int i, j;
        for(i = 0; i < verxs; i++) {
            graph.data[i] = data[i];
            for(j = 0; j < verxs; j++) {
                graph.weight[i][j] = weight[i][j];
            }
        }
    }

    public void showGraph(MGraph graph) {
        for(int[] link : graph.weight) {
            System.out.println(Arrays.toString(link));
        }
    }

    //得到最小生成树
    public void prim(MGraph graph, int v) {
        int visited[] = new int[graph.verxs];
        visited[v] = 1; //当前节点标记为已访问
        int h1 = -1; //记录两个顶点的下标
        int h2 = -1;
        int minWeight = 10000;
        for(int k = 1; k < graph.verxs; k++) {
            for(int i = 0; i < graph.verxs; i++) {
                for(int j = 0; j < graph.verxs; j++) {
                    if(visited[i] == 1 && visited[j] == 0 && graph.weight[i][j] < minWeight) {
                        minWeight = graph.weight[i][j];
                        h1 = i;
                        h2 = j;
                    }
                }
            }

            System.out.println("边<" + graph.data[h1] + ", " + graph.data[h2] + "权值：" + minWeight);

            visited[h2] = 1;//标记为已访问
            minWeight = 10000;
        }
    }
}

class MGraph{
    int verxs; //表示图的节点个数
    char[] data; //存放节点数据
    int[][] weight; //存放边

    public MGraph(int verxs) {
        this.verxs = verxs;
        data = new char[verxs];
        weight = new int[verxs][verxs];
    }
}
